Cyperus congestus

Tufted perennial with very short thick rhizome, often apparently annual. Culms triquetrous, smooth, slightly swollen at base, mostly 20–60 cm high, 1–3 mm diam. Leaves not septate-nodulose, shorter or longer than culms, 2–6 mm wide. Inflorescence simple or compound with 2–7 branches to 10 cm long, or head-like; spikes dense, broad-cylindric to hemispherical, 1–5 cm diam.; involucral bracts leaf-like, 2 or 3 longer than inflorescence. Spikelets flattened, numerous per spike, 10–28 mm long, 1–2 mm wide in side view, 8–24-flowered; rachilla winged, persistent; glumes acute, with sides 3–4-nerved, red-brown, c. 4 mm long; stamens 3; style 3-fid. Nut trigonous, narrow-obovoid, dark brown to black, c. one half as long as glume, c. 1.5 mm long, c. 0.6 mm diam. Flowers spring–summer.